Physicochemical quality of reservoir sediment in irrigation dams of Northern Ghana

Abstract

The present study assessed the physicochemical quality of irrigation dam reservoir sediment deposits for possible use in enriching soils in Northern Ghana. The surface area of the 9 study reservoirs was divided into upstream, midstream and downstream sections, with 18 undisturbed sediment samples taken at 0–30 cm depth for determining the soil dry bulk density, and 30 samples collected for analysis of particle size distribution, pH, macronutrients, CEC, EC, ESP and SAR. Reservoir sediments were rich in plant macronutrients (K, Ca and Mg) and organic matter and high in silt and clay content. The dry bulk density ranged from 1.10 ± 0.02 g/cm³ to 1.39 ± 0.08 g/cm³, while the sediment particle sizes were 10.3%–24.8% sand, 43.7%–53.1% silt and 30.6%–37.8% clay. The sediment pH ranged from a moderately acidic level of 5.48–6.64, with high levels of organic carbon (1.37%–2.96%) and organic matter (2.36%–5.10%). The total nitrogen (N) was found to be low (0.14%–0.29%), while the phosphorus (P) ranged from 2.6% to 4.9%, about 10 times higher than the FAO recommended normal average range. Except for the potassium (K) in two of the present study reservoirs, the exchangeable bases concentrations in the sediments were within acceptable levels for crop production. The CEC values were within moderate levels (13.69 to 29.84 cmol/kg), corresponding to a non-expanding, chemically inactive clay, while the salinity and sodicity were absent, with the EC varying between 0.03 and 0.27 dS/m and ESP ranging from 1.8% to 12.9%. Pearson's correlation analyses indicated both positive and negative relationships among the various physicochemical parameters. Based on the present study results, desilted irrigation reservoir sediments, being rich in all plant nutrients, except for N, appear to have great potential to enhance crop production for farmers.